The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
When a driver wants to change from one gear to another in a car with a manual transmission, the driver depresses a clutch pedal. The clutch disconnects the engine and interrupts power flow. Then the driver uses a manual stick shift to select another gear. The manual stick shift is connected by a mechanical linkage assembly to shift forks. The shift forks are attached to gear selectors, which deselect one gear and select another gear.
The gear selectors may include synchronizers to match a speed of the gear selector to the gear to prevent grinding. Once the new gear is engaged, the driver releases the clutch pedal to re-connect the engine and transmit power to the wheels.
As can be appreciated from the foregoing, manual transmissions do not provide a continuous flow of power from the engine to the wheels. Instead, power delivery changes from on to off (when the clutch is disengaged) and from off to on (when the clutch is engaged and the transmission is in gear). As can be appreciated, a loss of efficiency and reduced performance occurs during periods when the manual transmission is disengaged. Furthermore, the on/off nature of power delivery provided by the manual transmission can be annoying.
A dual-clutch transmission (DCT) uses two clutches but does not include a clutch pedal. One clutch may be used to control a first subset of gears (such as first, third, and fifth) while the other clutch may be used to control a second subset of the gears (such as second, fourth and sixth). Using this arrangement, a different gear can be preselected before the shift to prevent interruption in the power flow from the engine to the transmission. As a result, efficiency and performance is improved.
A powertrain control module and a hydraulic control system may be used to control operation of the clutches, shift forks and gear selectors. It is difficult to control the shift forks during synchronization and engagement or disengagement of the gear selectors. As a result, some DCTs may generate a banging noise when shifting. Furthermore, a significant amount of time and effort may be needed to calibrate the powertrain control module and hydraulic control system to shift with acceptable shift quality and speed.